Field research on nonhuman primates has documented the intra- and inter-specific variations in social structure and patterns of interaction in groups observed in different habitats. Theoretical formulations regarding differences have focused largely on the impact of diverse feeding ecologies. However, the influence of these ecological factors on Mother-infant relations and infant development, i.e. the ontogeny of these varied patterns, has not been considered systematically. Laboratory research on the other hand, while providing extensive quantitative data on development in a number of species has generally involved environments of minimal demand, or those of unusual environmental extremity, such as social isolation. Thus the role of the factors implicated most strongly in the field have largely been ignored in laboratory research of mother-infant relations and development. The current proposal, based on the concepts and data of primate field research and a variety of quantitative techniques derived from laboratory research, is an attempt to synthesize these approaches and provide systematic comparative data on the diverse effects of environmental (foraging) demand on Mother-infant relations and infant development in two closely related species of monkeys. Utilizing a laboratory simulation of foraging demand which has proven effective in extensive pilot work, this program will involve study of 2 groups each of pigtail and bonnet macaques, living under conditions of either high or low foraging demand conditions: within and across these environments we will assess intra- and inter-specific differences in group social patterns, mother-infant relations, infant social development, diurnal variations in behavior, time-budgets and the effects of these environments on infant affective and 'cognitive' development and the nature of kinship relations. This program should permit the formulation of more precise and more broadly applicable theory regarding environment-behavior transactions across the primate order, and assist in the the understanding of human development under diverse conditions.